This invention relates to railroad cars of the type commonly referred to as well cars and used to transport cargo containers. Well cars have a car body mounted on suitable trucks. The car body typically includes two side sills connected to draft sill assemblies. The side and draft sills define a well between the trucks. Container supports are attached to the side sills for supporting a container in the well. The well receives the container at about the lowest possible elevation above the track. Consequently, a loaded well car has a lower center of gravity compared to a standard flat car and admits the possibility of stacking two containers in a car.
The container supports, of course, have to transfer the weight of the container to the side sills. Since the vertical load of the container is applied at points located laterally inwardly of the side sills, bending moments are applied to the container supports, which in turn transfer the moments to the side sills. The situation with regard to bending moments is complicated by the fact that different container widths are used so the moment arm will vary. Providing a container support structure capable of withstanding the applied loads has been a troublesome matter in well car design.
Welded structures which essentially provide a support ledge at the bottom of the side sills have proven to be susceptible to fatigue failure. Attempts to combat the problem by simply making bigger support structures are costly both in terms of economics and space considerations. Large, bulky container supports leave less room for the container and have the undesirable consequence of raising the container position to make room for enlarged underlying supports. This to some extent defeats the purpose of the well car. Lindauer, U.S. Pat. No. 4,771,706, uses support castings to transfer the loads to the side sills.
A related problem of prior art container support structures is they transfer bending loads to the side sills. Consequently, the side sills must be designed to withstand not only the vertical loads imposed by the weight of the container but also the bending moment transferred to the sills by the container supports.